Hey there! :D
We know that <e <d and <c are supplementary. They are on a straight line and will equal 180 degrees.
We know F= 25 from the information.
Let's find a.
a= 4f+15
a= 4(25)+15
a= 115
Find b, which is supplementary to a and f.
25+115= 140
180-140= 40
We know that b is 40 degrees,
b and c are complementary, which means they equal 90 degrees.
90-40= 50
c= 50 degrees
Since b and e are vertical, they have the same measure.
b= 40 degrees.
So, 50+40= 90 degrees.
180-90= 90
<d= 90 degrees.
I hope this helps!
~kaikers